DESCRIPTION (from the application): There is compelling evidence that oxidative stress contributes to the age-related declines of important physiological functions. Studies have documented age-related impairment of mitochondrial respiration and enhanced production of a toxic product of lipid oxidation, HNE as well as oxidative stress related inhibitory modifications of COX and the adenine nucleotide transporter (ANT) by HNE. COX, a key component of the mitochondrial respiratory chain, declines with aging (as does ANT) and is damaged in diseases associated with the aging process. Additionally, while the underlying cause of age related oxidative stress remains to be defined, leakage of electrons from the bc 1 complex may be a primary source of reactive oxygen species within the mitochondrion. Thus, we hypothesize that age-related oxidative stress damages key components of the mitochondrial respiratory chain by oxidation of cardiolipin and by direct inhibition by HNE. Additionally, these inhibitory modifications can be mitigated by enhancement of mitochondrial antioxidant stores. Specific Aim 1 will establish HNE production and oxidative damage to cardiolipin as factors in the inhibition of COX, ANT, and bcl by aging. Experiments will determine effects of aging on production of HNE, distribution of HNE modifications of COX and bc 1 subunits and damage to the ANT molecule, formation of lipid hydroperoxides within mitochondria (focus on cardiolipin), and changes of antioxidant defenses that may predispose key mitochondrial proteins in the aging brain and liver to damage. Specific Aim 2 will establish HNE adduct formation and cardiolipin oxidation as specific means by which age related oxidative stress inhibits COX. It will address mechanisms by which specific age-related modifications of COX impair its activity. Studies will determine crosslinked and HNE labeled products of COX, identify specific sites of HNE labeling within each subunit, and quantify the role of cardiolipin oxidation in impaired COX activity. One rationale for SA2 is that it will directly link age-related effects on protein function to oxidative stress-mediated modification of the molecule. Specific Aim 3 will determine the roles of glutathione peroxidase4, Mn superoxide dismutase, glutathione, and a-tocopherol in protection of COX, ANT, and bcl from age-related modifications. Mitochondria from brains and livers of wild type and genetically altered mice will be used for all studies.